The present disclosure relates generally to equipment utilized and operations performed in conjunction with subterranean wells and, more particularly, to a control line connector assembly for downhole use.
In the oil and gas industry, control lines are often run along the exterior of production tubing or other wellbore tubulars extended into a wellbore to communicate between a surface location and a downhole location. The control lines, which may include optical fibers, electrical conductors, or hydraulic conduits, enable the transmission of signals, downhole data acquisition, activation and control of downhole devices, and numerous other applications. For example, command and control signals may be sent from a surface location downhole through a control line and to a downhole tool located within the wellbore. In other applications, downhole sensors collect data and relay that data to the surface location through a control line uplink for evaluation or use in the specific well-related operation. In yet other applications, hydraulic pressure is conveyed through the control lines to act on or otherwise actuate one or more downhole tools or devices.
Fiber optic control lines, in particular, can provide valuable downhole sensing means in a wellbore environment. For instance, optical fibers are often used to obtain distributed temperature measurements along all or a portion of the wellbore. When used as a temperature sensor, optical fibers provide a more complete temperature profile as compared to discrete temperature sensors.
Use of an optical fiber for distributed downhole temperature sensing may be highly beneficial during wellbore completion operations. In a stimulation operation, for instance, a temperature profile may be obtained to determine where injected fluid has entered surrounding formations or zones intersected by the wellbore. This information is useful in evaluating the effectiveness of the stimulation treatment and in planning future stimulation operations. Likewise, use of an optical fiber may also be highly beneficial during production operations. For example, a distributed temperature profile may be used in determining the location of water or gas influx along the sand control screens during production.
In a typical wellbore completion, lower portions of the completion string include various tools such as sand control screens, fluid flow control devices, and wellbore isolation devices. Various sensors, such as an optical fiber, may also be included in the lower portions of the completion string. After the completion process is finished, an upper portion of the completion string is separated from the lower portion of the completion string and retrieved to the surface, which simultaneously disconnects the optical fiber from surface communication. Accordingly, if information from the production zones is to be transmitted to the surface during production operations, a connection to the optical fiber in the completion string must be reestablished when production tubing string is installed. This can be done using either a dry or wet mate fiber optic connector, although wet mate connectors are more prevalent in downhole environments.
It has been found, however, that wet mating optical fibers in a downhole environment can be quite difficult. Currently, most wet mate connectors use a telescoping metal housing (including male and female portions) that locates, aligns, and washes the face of the connection. In operation, the male and female wet mate housings are first aligned, and then the respective wet mate faces are brought together axially. The male and female wet mate housings are then axially compressed such that an inner housing moves inside an outer housing and the optical fibers align internally within the housings. The telescoping inner and outer housings bring the end faces of each fiber in contact.
While generally able to establish optical communication between upper and lower ends of an optical fiber, conventional fiber optic connectors suffer from at least two inherent flaws. First, the mating faces of conventional fiber optic connectors are axially disposed and thereby increasingly prone to soiling by grease, scale, and other debris commonly encountered in the downhole environment. Second, a short length of fiber inside the fiber optic connector is subjected to column loading and is, therefore, prone to buckling or breaking.